CR cells turn by modulation of bilateral symmetry.
During phototaxis [1]} photons incident on the eyespot activate voltage-gated calcium channels
which alter levels of intracellular calcium, leading to
differential flagellar responses.
Ionic fluctuations (e.g. Ca\(^{2+}\) ) alter not only the flagellar beat,
but also the synchrony of a pair.
Gait changes involving transient loss of synchrony (called 'slips'),
occur stochastically at rates sensitive to such environmental factors [2]}, [3]}, [4]} as
temperature, light, chemicals, hydrodynamics, and age of cell culture.
In free-swimming cells, slips can alter the balance of hydrodynamic drag on the cell body,
producing a rocking motion that promotes subsequent resynchrony of flagella [5]},
but this does not explain the robust IP synchrony in cells held immobilized on micropipettes [6]}, [7]}, nor the
motility of isolated and reactivated flagellar apparatuses [8]}.
The altered beat during slips is analogous to the freestyle gait (AP in Fig. 1) characterized in the phototaxis
mutant ptx1, which stochastically transitions between IP and AP gaits [3]}, [7]}.
The dependence of CR flagellar synchronization state on physiology through temperature or ionic content of the medium [4]}
leads us now to the possibility for intracellular coupling of flagella.
<FIGURE>